Method for the production of glass threads coated with a thermofusible size and products resulting therefrom

ABSTRACT

The present invention relates to a process for producing glass strands coated with a hot-melt size, whereby molten glass streams, flowing out of orifices located in the base of one or more bushings, are drawn in the form of one or more sheets of continuous filaments, the filaments are then assembled into one or more strands that are collected on one or more moving supports, this process consisting in depositing a first composition containing a coupling agent on the glass filaments and then in depositing a second composition comprising a hot-melt polymer in the melt state, at the latest during assembly of the filaments into one or more strands. It also relates to the glass strands obtained according to this process and to the composites containing said strands.

The present application is the national stage application of WO04/085331, the text of which is hereby incorporated by reference andclaims priority of the French Application No. 03/03685 filed on Mar. 21,2003.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 371 of PCT/FR04/00646 filed Mar. 17, 2004and claims priority to FR 03/03685 filed Aug. 1, 2008.

The present invention relates to the manufacture of reinforcing strandsused in the construction of composites. It relates more precisely to aprocess for producing glass strands coated with a hot-melt size, andalso to the strands obtained and to the composites produced from saidstrands.

It is known to manufacture glass reinforcing strands from streams ofmolten glass that flow out of the numerous orifices of a bushing. Thesestrands are drawn into continuous filaments, they are then possiblycombined with filaments of another material, before being assembled intostrands that are collected, usually in the form of wound packages.

Before they are assembled in the form of strands, the glass filamentspass through a device for coating them with a size or sizingcomposition. Deposition of the size is essential. Firstly, it allows astrand to be obtained with the filaments protected from abrasion bycontact with the various processing members, thereby preventing themfrom breaking during manufacture and possibly during their use.Secondly, the size allows the strand to be combined with the organicand/or inorganic materials to be reinforced, by making it easier for thestrands to be wetted by and impregnated with these materials.

As a general rule, the size increases the adhesion between the glass andthe materials to be reinforced, resulting in improved mechanicalproperties. The size also promotes mutual cohesion of the filaments,thereby resulting in better integrity of the strand, this property beingespecially desirable in textile applications where the strands mustwithstand high mechanical stresses during weaving.

The sizing compositions most commonly used are aqueous compositions(with more than 85% water by weight) containing compounds that arecapable of crosslinking subsequent to deposition on the filaments,especially under the effect of a heat treatment carried out after thestrands have been collected together. Easy to produce and to deposit,these sizing compositions are also very stable and do not cureprematurely, which would make deposition impossible, whether duringstorage or beneath the bushing.

In order for the strands to be effectively combined with the materialsto be reinforced, it is necessary, however, to remove the water, thisgenerally being achieved by drying the wound strand packages in ovens.However, this treatment is not entirely satisfactory because, on the onehand, it is expensive (the investment costs in terms of ovens and theoperating costs, in particular those associated with energy consumption,are considerable) and, on the other hand, it causes the components ofthe size to migrate to the outside of the package, resulting in a strandof variable quality. In the case of composite strands, which combineglass filaments with filaments of a thermoplastic organic material, itmay happen that the organic filaments have a change-of-state temperature(for example a glass transition temperature) close to 100° C., whichprecludes heating these strands to a temperature high enough to removethe water therefrom.

One solution that avoids drying consists in using a hot-melt size basedon a thermoplastic polymer which has the property of being liquid whenit is heated and of solidifying upon cooling. Such a size, applied hot(at a temperature above its solidification temperature), makes itpossible for those filaments to be more or less completely sheathed. Thechoice of the nature of the polymer depends on the matrix to bereinforced and/or on the organic filaments combined in the compositestrand; there is a direct influence on the processibility of the strandand on the mechanical performance level of the composite materialsproduced from these strands.

A drawback of hot-melt polymers lies in their insufficient ability tobond correctly to glass. In the case of composite strands, this resultsin poor cohesion of the filaments, which tend to group togetherdepending on their nature, hence resulting in segregation that may leadto the formation of loops. In some applications, such as weaving, thisstrand cannot be used because knots form, which cause the weavingmachines to stop.

To remedy this drawback, it proves necessary to add at least onecoupling agent to the size deposited on the glass. The coupling agentmust have an affinity both for the glass and for the matrix to bereinforced, and possibly for the filaments other than the glassfilaments when the strands are composite strands. The coupling agentmust also be compatible with the constituents of the size without,however, prematurely reacting with them, which would cause a substantialincrease in the viscosity, or even complete gelling, and would makedeposition on the glass impossible.

The object of the present invention is to provide a process forproducing glass strands sized by compositions that contain at least onecoupling agent and a hot-melt polymer, this process preventing prematureor inopportune reactions between these constituents and requiring nodrying.

This object is achieved by the process according to the inventionwhereby molten glass streams, flowing out of orifices located in thebase of one or more bushings, are drawn in the form of one or moresheets of continuous filaments, the filaments are then assembled intoone or more strands that are collected on one or more moving supports,this process consisting in depositing a first composition containing acoupling agent on the glass filaments and then in depositing a secondcomposition comprising a hot-melt polymer in the melt state on saidfilaments, at the latest during assembly of the filaments into one ormore strands.

The process according to the invention has several advantages. It uses asize involving little or no water, which therefore obviates stranddrying treatments, and therefore representing a major saving. Itimproves the bonding of the coupling agent to the glass. Since thecoupling agent is applied first, there is thus enough time for it toreact with the glass before coming into contact with the hot-meltpolymer. Similarly, since the coupling agent is deposited separately,the final amount on the strand may be precisely adjusted. The processlimits the loss of the coupling agent by evaporation since the latter isapplied at room temperature (that is to say without supplying additionalenergy) to cooled filaments, and consequently the risk of inhalation oftoxic substances by the operators is kept at a very low level and thereis a substantial saving (the coupling agent generally representing asubstantial portion of the cost of the size).

The process according to the invention, thanks to the advantages that itaffords, allows strands to be obtained with a uniform quality over theirentire length.

In particular, this simply implemented process offers great freedom inchoosing the coupling agent and the hot-melt polymer because they areintroduced separately onto the filaments. It thus simplifies thepreparation of the sizing compositions, this often being tricky owing tothe problems of compatibility and/or homogenization of the constituents,which problems may be accentuated during storage and deposition of thesize. Moreover, the process applies with the same advantages to theproduction of various types of glass-based sized strands as indicatedbelow.

In the present invention, the term “glass strands” is understood to meanglass-based strands, that is to say not only strands formed solely fromglass filaments, but also strands formed from glass filaments andfilaments of a thermoplastic organic material. In the latter case, whilethe glass filaments are being drawn, the formed filaments of organicmaterial are extruded from an extrusion head and simultaneouslyentrained (or the strands of organic material are fed in at the sametime from, for example, packages), the paths followed by the glassfilaments and the filaments (or strands) of organic material convergingon one another before said filaments are assembled into at least onemechanically entrained composite strand.

The glass filaments may be drawn in the form of a sheet from a bushingor in the form of several sheets from one or more bushings and may beassembled into one or more strands. The drawing speed of the glassfilaments in the process according to the invention is generally between6 and 50, preferably 9 and 20, meters per second.

According to the invention, the compositions, in particular thecomposition containing the coupling agent (first composition), aregenerally deposited on cooled glass filaments, that is to say thosehaving a temperature not exceeding 90° C., preferably 75° C., in orderto avoid any risk of selective evaporation and to allow better controlof the amount of material deposited on the filaments. Optionally, thecooling of the filaments may be speeded up by spraying an appropriatefluid, for example by spraying water which evaporates naturally beforethe coupling agent is deposited, and/or by blowing air.

The first composition containing the coupling agent is deposited whilethe glass filaments are being drawn, but before they are assembled intostrands, so as to prevent them from breaking on the assembling device.Preferably, the first composition is deposited as soon as the filamentshave reached the cooling temperature indicated above so as to have themaximum possible time for contact between the glass and the couplingagent. This increases the bonding of the coupling agent before thesecond composition, which contains the hot-melt polymer, is applied. Theapplication may take place, for example, using a sizing roller, a lippeddevice or a sprayer. Preferably, a sizing roller is used.

The deposition of the second composition containing the hot-melt polymertakes place after the filaments have been coated with the firstcomposition, and at the latest while the filaments are being assembledinto strands. The deposition may be carried out using the same devicesas those used for the first composition, these also having to beprovided with means for keeping the hot-melt polymer in the melt state.The temperature for applying the hot-melt composition is generally lessthan or equal to 200° C., is preferably less than or equal to 160° C.and better still is greater than 100° C. The temperature is chosen sothat the viscosity of the hot-melt composition is low enough for it tobe correctly deposited on the glass filaments and for the residualtraces of water to be able to be removed. These requirements aresatisfied with a viscosity of around 200 to 600 mPa·s, preferably 300 to500 mPa·s. The aforementioned temperature conditions furthermore reducethe risk of the polymer undergoing thermal degradation that may impairits properties, while nevertheless maintaining a reasonable energyconsumption and satisfactory safety conditions for the operators.

The composition applied firstly to the glass filaments comprises one ormore coupling agents capable of bonding to the glass and of promotingbonding of the hot-melt polymer deposited subsequently. The couplingagent may be chosen, for example, from organofunctional silanes,especially those containing one or more hydrolysable groups, such asγ-aminopropyltriethoxysilane, γ-glycidoxy-propyltrimethoxysilane,γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, titanatesand zirconates. The preferred coupling agent isγ-aminopropyltriethoxysilane.

The first composition may furthermore include a diluent that helps todissolve the coupling agent or agents. The optional diluents areessentially water and any organic compound having, where appropriate, atleast one particular function in the size, such as filament protection,strand flexibility, etc. Preferably, the composition contains no organicsolvent for toxicity and volatile organic compound (VOC) emissionreasons. More preferably, the composition contains water in an amount aslow as possible but nevertheless sufficient for deposition underacceptable conditions and such that the water, once the composition hasbeen deposited, can evaporate naturally, without supplying furtherenergy.

The coupling agent concentration in the composition depends on theapplication conditions, especially the speed at which the glassfilaments are drawn and on the device used for the deposition. Forexample, good results are obtained with an aqueous compositioncomprising at least 5% by weight of coupling agent deposited on thefilaments running at a speed of around 9 to 17 meters per second bymeans of a sizing roller.

The second composition may comprise one or more polymers that can bedeposited under the conditions of the process and can resist thermaldegradation. The hot-melt polymers may be chosen from polymers that aresolid at a temperature below 50° C. and have a viscosity of between 200and 600 mPa·s, preferably between 300 and 500 mPa·s, at the depositiontemperature, which is generally around 100 to 200° C.

The choice of polymer essentially depends on the material to bereinforced. In particular, it is important for the polymer to becompatible with said material when it is desirable for the finalcomposite to have good levels of mechanical performance.

When the strand is a composite strand, the choice also depends on thenature of the thermoplastic filaments used. In particular, it isnecessary to ensure that the hot-melt polymer is compatible with thesefilaments, thereby preventing repulsion effects leading to the filamentsbunching together according to their nature (glass or thermoplastic) andtherefore being distributed nonuniformly within the strand.

For example, when the thermoplastic filaments essentially consist of oneor more polyolefins, such as polyethylene or polypropylene, the hot-meltpolymer is a copolymer of ethylene and/or propylene with acrylic acid ormaleic anhydride.

When these same filaments essentially consist of one or morethermoplastic polyesters, such as polyethylene terephthalate (PET) orpolybutylene terephthalate (PBT), the hot-melt polymer may be an epoxy,for example one belonging to the DGEBA (diglycidyl ether of bisphenyl A)group.

The amount of hot-melt polymer deposited on the glass filamentsrepresents in general 2 to 15%, preferably 3 to 8%, by weight of theglass. Above 15%, the state of solidification of the polymer on thefilaments before they are assembled in the form of a strand is notcomplete, which results in substantial bonding between the filaments.The strand obtained is unusable as it lacks flexibility.

The second composition may furthermore include a diluent for adaptingthe viscosity to the deposition conditions. This is usually a polymer ofa similar nature to the hot-melt polymer, but one that is incapable ofreacting with the coupling agent, for example a wax, especially apolyolefin wax.

The compositions deposited on the glass filaments may furthermoreinclude one or more compounds conferring particular properties on thesize. These compounds (denoted hereafter by the term additives) may beprovided by one or other of the compositions, preferably by the hot-meltcomposition.

As additives, mention may especially be made of:

-   -   lubricants, preferably nonionic lubricants;    -   antistatic agents;    -   antioxidants;    -   UV stabilizers;    -   nucleating agents;    -   pigments.

Preferably, the content of agents of each of the aforementionedcategories is less than or equal to 1% by weight of the size andadvantageously the total content of additives is less than 5%.

The choice of coupling agent and of hot-melt polymer, and also theiramounts, depends in particular on the material to be reinforced by thestrands according to the invention and on the intended application.

As a general rule, the total amount of the compositions deposited on theglass filaments represents 2 to 15%, preferably 3 to 8%, by weight ofthe glass.

The glass filaments coated with the size may be combined with filamentsof a thermoplastic organic material before being assembled to form oneor more composite strands. The combining operation is generally carriedout by spraying the thermoplastic filaments into the sheet of glassfilaments in order to obtain comingling of the filaments. The sprayingmay be carried out by any known means for fulfilling this role, forexample a Venturi device.

The constituent thermoplastic material of the filaments may be chosenfrom materials capable of giving filaments, especially by extrusion in adevice such as an extrusion head. As examples, mention may be made ofpolyolefins, such as polyethylene and polypropylene, thermoplasticpolyesters, such as polyethylene terephthalate (PET) and polybutyleneterephthalate (PBT), polyethers and polyamides, such as nylon-11 andnylon-12.

The strands are generally collected in the form of packages wound ontorotating supports, for example to form bobbins of continuous strands.

They may also be collected on receiving supports moving translationally,allowing a mat of continuous or chopped intermingled strands to beformed. To do this, it is possible to use, for example, a device forspraying the strands toward the collecting surface that is movingtransversely to the direction of the sprayed strands, said device alsoallowing the strands to be drawn and optionally chopped.

The strands obtained according to the invention may thus be in variousforms after collection: bobbins of continuous strands (rovings orcakes), chopped strands and assemblies (mats or networks). Afterconversion, they may be in the form of tapes, braids and fabrics.

The glass filaments forming these strands have a diameter of between 10and 30 microns, preferably between 14 and 23 microns, and the glass maybe any glass known for producing reinforcing strands, for exampleE-glass, AR (alkali-resistant)-glass, R-glass or S-glass. E- andAR-glasses are preferred.

When the strand consists only of glass, its linear density may varybetween 200 and 4000 tex, preferably 640 and 2000 tex.

In the case of composite strands, the glass content may vary from 30 to85%, preferably 53 to 83%, by weight of the strand.

At room temperature, the strands obtained are coated with a solidifiedsize, the weight content of which is constant over the entire length ofthe strand.

The strands according to the invention may be combined with variousmaterials to be reinforced, especially with a view to producingcomposite components having good mechanical properties. The compositesare advantageously obtained by combining at least strands according tothe present invention with at least one thermoplastic organic material,such as polyolefins, polyvinylchlorides (PVCs) and polyesters.

The glass content in the composites is generally between 20 and 80%,preferably 28 and 60%, by weight.

The following examples will be used to illustrate the invention without,however, limiting it.

EXAMPLE 1

E-glass filaments 18.5 μm in diameter, obtained from streams of glassoutput by a bushing having 800 orifices, were mechanically drawn at aspeed of 14 m/s.

Along their path, they were coated with an aqueous solution containing16.10 wt % γ-amino propyltriethoxysilane (SILQUEST A 1100, sold byCrompton) in contact with a sizing roller. The ambient temperaturearound the roller was about 40° C.

The filaments then passed over a second sizing roller placedapproximately 30 cm from the first, and heated to 140° C., whichdelivered a composition containing 70 wt % of an ethylene/acrylic acidcopolymer (AC 540, sold by Honeywell) and 30 wt % of polyethylene (AC617, sold by Honeywell).

Polypropylene filaments extruded from an extrusion head having 600 holespassed through a Venturi device that sprayed them into the sheet ofglass filaments after it had passed over the second sizing roller. Theintimately mixed glass and polypropylene filaments were then assembledinto a single strand, which was wound in the form of a roving.

The strand obtained comprised 60 wt % of glass filaments having a losson ignition of 4%.

This strand could be easily handled—it was flexible and integral, andhad a uniform coating over its entire length and good distribution ofthe glass filaments and polypropylene filaments within the strand, thatis to say substantial comingling of all the filaments. It could also bewoven, and the woven fabric obtained could be used to reinforcethermoplastic organic materials, especially polyolefins (PE and PP).

EXAMPLE 2 (COMPARATIVE EXAMPLE)

This example was produced under the same conditions as for Example 1,but modified in that the two compositions were premixed in order to forma single composition, which was deposited on the filaments by means ofthe heated sizing roller.

The composition obtained had a very high viscosity, making it impossibleto be applied to the filaments using a sizing roller.

EXAMPLE 3

E-glass filaments 18.5 μm in diameter, obtained from streams of glassoutput by a bushing having 800 orifices, were mechanically drawn at aspeed of 14 m/s.

Along their path, they were coated with an aqueous solution containing16.10 wt % γ-amino propyltriethoxysilane (SILQUEST A 1100, sold byCrompton) in contact with a sizing roller. The ambient temperaturearound the roller was about 40° C.

The filaments then passed over a second sizing roller placedapproximately 30 cm from the first, and heated to 140° C., whichdelivered a DGEBA-type epoxy polymer (DER 671 sold by Dow Chemical).

Polyethylene terephthalate filaments extruded from an extrusion headhaving 600 holes passed through a Venturi device that sprayed them intothe sheet of glass filaments after it had passed over the second sizingroller. The intimately mixed glass and polyethylene terephthalatefilaments were then assembled into a single strand, which was wound inthe form of a roving.

The strand obtained consisted of 65% glass. It was easy to handle andhad properties similar to those of the strand of Example 1.

This strand could be used as reinforcement in PVC, especially for theproduction of sections for windows.

1. A process for producing sized glass strands, comprising providing molten glass streams, flowing out of orifices located in the base of one or more bushings, and which are drawn in the form of one or more sheets of continuous glass filaments, depositing a first composition containing a coupling agent on single glass filaments, subsequent to the deposition of first composition, depositing a second composition comprising a hot-melt polymer in the melt state on said single glass filaments, assembling the single glass filaments into one or more strands that are collected on one or more moving supports, wherein the second composition is deposited prior to or at the same time as the assembly of the single glass filaments into one or more strands.
 2. The process as claimed in claim 1, wherein the first composition is deposited on the single glass filaments cooled to a temperature not exceeding 90° C.
 3. The process as claimed in claim 2, wherein the cooling of the single glass filaments is speeded up by spraying a fluid, by spraying water or by blowing air.
 4. The process as claimed in claim 1, wherein the coupling agent is at least one selected from the group consisting of organofunctional silanes, organofunctional silanes containing one or more hydrolizable groups, titanates and zirconates.
 5. The process as claimed in claim 4, wherein the coupling agent is γ-aminopropyltriethoxysilane.
 6. The process as claimed in claim 1, wherein the second composition is deposited at a temperature of less than or equal to 200° C.
 7. The process as claimed in claim 1, wherein the viscosity of the second composition is around 200 to 600 mPas at a temperature between 100 and 200° C.
 8. The process as claimed in claim 1, wherein the hot-melt polymer is solid at a temperature below 50° C.
 9. The process as claimed in claim 1, wherein the single glass filaments are combined with filaments of a thermoplastic organic material before they are assembled in the form of one or more strands.
 10. The process as claimed in claim 9, wherein the thermoplastic organic material is at least one selected from the group consisting of polyolefins, thermoplastic polyesters, polyesters and polyamides.
 11. The process as claimed in claim 1, wherein the compositions deposited on the strand furthermore include at least one additive selected from the group consisting of lubricants, antistatic agents, antioxidants, UV stabilizers, nucleating agents and pigments.
 12. The process as claimed in claim 1, wherein the total amount of the compounds deposited on the single glass filaments represents 2 to 15% by weight of the glass.
 13. A glass strand coated with a thermoplastic sizing composition as obtained by the process as claimed in claim
 1. 14. A composite comprising at least one thermoplastic organic material and sized glass strands, wherein the composite comprises, at least in part, sized glass strands as claimed in claim
 13. 15. The composite as claimed in claim 14, wherein the thermoplastic organic material is at least one selected from the group consisting of polyolefins, polyvinyl chlorides and polyesters.
 16. The composite as claimed in claim 14, wherein the composite has a glass content of between 20 and 80%.
 17. The process as claimed in claim 1, wherein the viscosity of the second composition is around 300 to 500 mPas at a temperature between 100 and 200° C. 